Si I use 4 liter, 7 liter, and 12.5 liter airpots. I honestly think for bang for the buck and yield the 4 liter pots are ideal. I have 3 plants in the 4 liter and they will all yield 2-4 ounces a piece easy. There is a couple of factors determining pot size imo. First and most importantly is humidity. I will never us an airpot over 7 liters in the summer anymore. Takes to long to dry and for the roots to set even with a dehumidifier. So smaller pots work better in high humidity. The reverse is true in low humidity. So 4 liter pots dry out every day now, 7 liter 2 days, and 12 liter every 3-4 days. So I think tailoring the pot size to environmental conditions not to yield will benefit any grower greatly! Also you will see fewer issues since the pots will dry evenly as well.